FirForLoopChecker: report also OPERATOR_MODIFIER if appropriate + minor

This commits checks iterator/hasNext/next functions whether they are
declared as operator or not. Also, it changes logic of hasNext/next
error reporting, now we're able to report errors about both these
functions.

compiler/fir/analysis-tests/testData/resolveWithStdlib/diagnostics/forLoopChecker.fir.txt

@@ -143,6 +143,16 @@ FILE: forLoopChecker.kt
 
         public abstract operator fun next(): R|kotlin/Int|
 
+    }
+    public abstract class ImproperIterator6 : R|kotlin/Any| {
+        public constructor(): R|ImproperIterator6| {
+            super<R|kotlin/Any|>()
+        }
+
+        public abstract fun hasNext(): R|kotlin/Boolean|
+
+        public abstract fun next(): R|kotlin/Int|
+
     }
     public abstract class NotRange8 : R|kotlin/Any| {
         public constructor(): R|NotRange8| {
@@ -152,7 +162,15 @@ FILE: forLoopChecker.kt
         public abstract operator fun iterator(): R|ImproperIterator5|
 
     }
-    public final fun test(notRange1: R|NotRange1|, notRange2: R|NotRange2|, notRange3: R|NotRange3|, notRange4: R|NotRange4|, notRange5: R|NotRange5|, notRange6: R|NotRange6|, notRange7: R|NotRange7|, notRange8: R|NotRange8|, range0: R|Range0|, range1: R|Range1|): R|kotlin/Unit| {
+    public abstract class NotRange9 : R|kotlin/Any| {
+        public constructor(): R|NotRange9| {
+            super<R|kotlin/Any|>()
+        }
+
+        public abstract fun iterator(): R|ImproperIterator6|
+
+    }
+    public final fun test(notRange1: R|NotRange1|, notRange2: R|NotRange2|, notRange3: R|NotRange3|, notRange4: R|NotRange4|, notRange5: R|NotRange5|, notRange6: R|NotRange6|, notRange7: R|NotRange7|, notRange8: R|NotRange8|, notRange9: R|NotRange9|, range0: R|Range0|, range1: R|Range1|): R|kotlin/Unit| {
         lval <iterator>: R|ERROR CLASS: Unresolved name: iterator| = R|<local>/notRange1|.<Unresolved name: iterator>#()
         while(R|<local>/<iterator>|.<Unresolved name: hasNext>#()) {
             lval i: R|ERROR CLASS: Unresolved name: next| = R|<local>/<iterator>|.<Unresolved name: next>#()
@@ -193,6 +211,11 @@ FILE: forLoopChecker.kt
             lval i: R|kotlin/Int| = R|<local>/<iterator>|.R|/ImproperIterator5.next|()
         }
 
+        lval <iterator>: R|ImproperIterator6| = R|<local>/notRange9|.R|/NotRange9.iterator|()
+        while(R|<local>/<iterator>|.R|/ImproperIterator6.hasNext|()) {
+            lval i: R|kotlin/Int| = R|<local>/<iterator>|.R|/ImproperIterator6.next|()
+        }
+
         lval <iterator>: R|GoodIterator| = R|<local>/range0|.R|/Range0.iterator|()
         while(R|<local>/<iterator>|.R|/GoodIterator.hasNext|()) {
             lval i: R|kotlin/Int| = R|<local>/<iterator>|.R|/GoodIterator.next|()

compiler/fir/analysis-tests/testData/resolveWithStdlib/diagnostics/forLoopChecker.kt

@@ -70,20 +70,42 @@ abstract class ImproperIterator5 {
     abstract operator fun next() : Int
 }
 
+abstract class ImproperIterator6 {
+    abstract fun hasNext() : Boolean
+    abstract fun next() : Int
+}
+
 abstract class NotRange8() {
     abstract operator fun iterator() : ImproperIterator5
 }
 
+abstract class NotRange9() {
+    abstract fun iterator(): ImproperIterator6
+}
 
-fun test(notRange1: NotRange1, notRange2: NotRange2, notRange3: NotRange3, notRange4: NotRange4, notRange5: NotRange5, notRange6: NotRange6, notRange7: NotRange7, notRange8: NotRange8, range0: Range0, range1: Range1) {
+
+fun test(
+    notRange1: NotRange1,
+    notRange2: NotRange2,
+    notRange3: NotRange3,
+    notRange4: NotRange4,
+    notRange5: NotRange5,
+    notRange6: NotRange6,
+    notRange7: NotRange7,
+    notRange8: NotRange8,
+    notRange9: NotRange9,
+    range0: Range0,
+    range1: Range1
+) {
     for (i in <!ITERATOR_MISSING!>notRange1<!>);
-    for (i in <!HAS_NEXT_MISSING!>notRange2<!>);
+    for (i in <!HAS_NEXT_MISSING, NEXT_MISSING!>notRange2<!>);
     for (i in <!NEXT_MISSING!>notRange3<!>);
     for (i in <!HAS_NEXT_MISSING!>notRange4<!>);
     for (i in notRange5);
     for (i in notRange6);
     for (i in notRange7);
     for (i in <!HAS_NEXT_MISSING!>notRange8<!>);
+    for (i in <!OPERATOR_MODIFIER_REQUIRED, OPERATOR_MODIFIER_REQUIRED, OPERATOR_MODIFIER_REQUIRED!>notRange9<!>);
     for (i in range0);
     for (i in range1);
 }

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -185,6 +185,10 @@ object DIAGNOSTICS_LIST : DiagnosticList() {
             parameter<KtModifierKeywordToken>("modifier")
             parameter<String>("target")
         }
+        val OPERATOR_MODIFIER_REQUIRED by error<FirSourceElement, PsiElement> {
+            parameter<FirNamedFunctionSymbol>("functionSymbol")
+            parameter<String>("name")
+        }
     }
 
     val INLINE_CLASSES by object : DiagnosticGroup("Inline classes") {

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt

@@ -24,6 +24,7 @@ import org.jetbrains.kotlin.fir.declarations.FirValueParameter
 import org.jetbrains.kotlin.fir.expressions.FirExpression
 import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
@@ -173,6 +174,7 @@ object FirErrors {
     val INCOMPATIBLE_MODIFIERS by error2<PsiElement, KtModifierKeywordToken, KtModifierKeywordToken>()
     val REDUNDANT_OPEN_IN_INTERFACE by warning0<KtModifierListOwner>(SourceElementPositioningStrategies.OPEN_MODIFIER)
     val WRONG_MODIFIER_TARGET by error2<PsiElement, KtModifierKeywordToken, String>()
+    val OPERATOR_MODIFIER_REQUIRED by error2<FirSourceElement, PsiElement, FirNamedFunctionSymbol, String>()
 
     // Inline classes
     val INLINE_CLASS_NOT_TOP_LEVEL by error0<KtDeclaration>(SourceElementPositioningStrategies.INLINE_OR_VALUE_MODIFIER)

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirForLoopChecker.kt

@@ -19,16 +19,20 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.ITERATOR_ON_NULLA
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NEXT_AMBIGUITY
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NEXT_MISSING
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NEXT_NONE_APPLICABLE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.OPERATOR_MODIFIER_REQUIRED
 import org.jetbrains.kotlin.fir.declarations.FirProperty
+import org.jetbrains.kotlin.fir.declarations.isOperator
 import org.jetbrains.kotlin.fir.expressions.FirBlock
 import org.jetbrains.kotlin.fir.expressions.FirFunctionCall
 import org.jetbrains.kotlin.fir.expressions.FirWhileLoop
 import org.jetbrains.kotlin.fir.references.FirErrorNamedReference
+import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
 import org.jetbrains.kotlin.fir.resolve.calls.InapplicableWrongReceiver
 import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeAmbiguityError
 import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeInapplicableCandidateError
 import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeUnresolvedNameError
 import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.resolve.calls.tower.isSuccess
 
@@ -54,18 +58,15 @@ object FirForLoopChecker : FirBlockChecker() {
                 continue
             }
             val hasNextCall = whileLoop.condition as FirFunctionCall
-            if (checkSpecialFunctionCall(
-                    hasNextCall,
-                    reporter,
-                    source,
-                    context,
-                    HAS_NEXT_FUNCTION_AMBIGUITY,
-                    HAS_NEXT_MISSING,
-                    noneApplicableFactory = HAS_NEXT_FUNCTION_NONE_APPLICABLE
-                )
-            ) {
-                continue
-            }
+            checkSpecialFunctionCall(
+                hasNextCall,
+                reporter,
+                source,
+                context,
+                HAS_NEXT_FUNCTION_AMBIGUITY,
+                HAS_NEXT_MISSING,
+                noneApplicableFactory = HAS_NEXT_FUNCTION_NONE_APPLICABLE
+            )
             val elementDeclaration = whileLoop.block.statements.firstOrNull() as? FirProperty ?: continue
             if (elementDeclaration.initializer?.source?.kind != FirFakeSourceElementKind.DesugaredForLoop) continue
             val nextCall = elementDeclaration.initializer as FirFunctionCall
@@ -91,33 +92,48 @@ object FirForLoopChecker : FirBlockChecker() {
         noneApplicableFactory: FirDiagnosticFactory1<FirSourceElement, KtExpression, Collection<AbstractFirBasedSymbol<*>>>? = null,
         unsafeCallFactory: FirDiagnosticFactory0<FirSourceElement, KtExpression>? = null,
     ): Boolean {
-        val calleeReference = call.calleeReference
-        if (calleeReference is FirErrorNamedReference) {
-            when (val diagnostic = calleeReference.diagnostic) {
-                is ConeAmbiguityError -> if (diagnostic.applicability.isSuccess) {
-                    reporter.reportOn(reportSource, ambiguityFactory, diagnostic.candidates, context)
-                } else if (noneApplicableFactory != null) {
-                    reporter.reportOn(reportSource, noneApplicableFactory, diagnostic.candidates, context)
-                }
-                is ConeUnresolvedNameError -> {
-                    reporter.reportOn(reportSource, missingFactory, context)
-                }
-                is ConeInapplicableCandidateError -> {
-                    if (unsafeCallFactory != null || noneApplicableFactory != null) {
-                        diagnostic.candidate.diagnostics.filter { it.applicability == diagnostic.applicability }.forEach {
-                            if (it is InapplicableWrongReceiver) {
-                                if (unsafeCallFactory != null) {
-                                    reporter.reportOn(reportSource, unsafeCallFactory, context)
-                                } else {
-                                    reporter.reportOn(reportSource, noneApplicableFactory!!, listOf(diagnostic.candidate.symbol), context)
+        when (val calleeReference = call.calleeReference) {
+            is FirErrorNamedReference -> {
+                when (val diagnostic = calleeReference.diagnostic) {
+                    is ConeAmbiguityError -> if (diagnostic.applicability.isSuccess) {
+                        reporter.reportOn(reportSource, ambiguityFactory, diagnostic.candidates, context)
+                    } else if (noneApplicableFactory != null) {
+                        reporter.reportOn(reportSource, noneApplicableFactory, diagnostic.candidates, context)
+                    }
+                    is ConeUnresolvedNameError -> {
+                        reporter.reportOn(reportSource, missingFactory, context)
+                    }
+                    is ConeInapplicableCandidateError -> {
+                        if (unsafeCallFactory != null || noneApplicableFactory != null) {
+                            diagnostic.candidate.diagnostics.filter { it.applicability == diagnostic.applicability }.forEach {
+                                if (it is InapplicableWrongReceiver) {
+                                    if (unsafeCallFactory != null) {
+                                        reporter.reportOn(
+                                            reportSource, unsafeCallFactory, context
+                                        )
+                                    } else {
+                                        reporter.reportOn(
+                                            reportSource, noneApplicableFactory!!, listOf(diagnostic.candidate.symbol), context
+                                        )
+                                    }
+                                    return true
                                 }
-                                return true
                             }
                         }
                     }
                 }
+                return true
+            }
+            is FirResolvedNamedReference -> {
+                val symbol = calleeReference.resolvedSymbol
+                if (symbol is FirNamedFunctionSymbol) {
+                    val function = symbol.fir
+                    if (!function.isOperator) {
+                        reporter.reportOn(reportSource, OPERATOR_MODIFIER_REQUIRED, symbol, function.name.asString(), context)
+                        // Don't return true as we want to report other errors
+                    }
+                }
             }
-            return true
         }
         return false
     }

compiler/testData/diagnostics/tests/ForRangeConventions.fir.kt

@@ -79,7 +79,7 @@ abstract class NotRange8() {
 
 fun test(notRange1: NotRange1, notRange2: NotRange2, notRange3: NotRange3, notRange4: NotRange4, notRange5: NotRange5, notRange6: NotRange6, notRange7: NotRange7, notRange8: NotRange8, range0: Range0, range1: Range1) {
   for (i in <!ITERATOR_MISSING!>notRange1<!>);
-  for (i in <!HAS_NEXT_MISSING!>notRange2<!>);
+  for (i in <!HAS_NEXT_MISSING, NEXT_MISSING!>notRange2<!>);
   for (i in <!NEXT_MISSING!>notRange3<!>);
   for (i in <!HAS_NEXT_MISSING!>notRange4<!>);
   for (i in notRange5);

compiler/testData/diagnostics/tests/Operators.fir.kt

@@ -111,4 +111,31 @@ fun test2() {
     Anc() + Anc()
     Anc() - Anc()
     Anc2() + Anc2()
-}
+}
+
+fun Int.iterator(): MyIntIterator = null!!
+
+operator fun Double.iterator(): MyDoubleIterator = null!!
+
+operator fun Boolean.iterator(): MyBooleanIterator = null!!
+
+interface MyIntIterator {
+    operator fun hasNext(): Boolean
+    operator fun next(): Int
+}
+
+interface MyDoubleIterator {
+    operator fun hasNext(): Boolean
+    fun next(): Double
+}
+
+interface MyBooleanIterator {
+    fun hasNext(): Boolean
+    operator fun next(): Boolean
+}
+
+fun test3(i: Int, d: Double, b: Boolean) {
+    for (element in <!OPERATOR_MODIFIER_REQUIRED!>i<!>) {}
+    for (element in <!OPERATOR_MODIFIER_REQUIRED!>d<!>) {}
+    for (element in <!OPERATOR_MODIFIER_REQUIRED!>b<!>) {}
+}

compiler/testData/diagnostics/tests/Operators.kt

@@ -111,4 +111,31 @@ fun test2() {
     Anc() + Anc()
     Anc() <!OPERATOR_MODIFIER_REQUIRED!>-<!> Anc()
     Anc2() + Anc2()
-}
+}
+
+fun Int.iterator(): MyIntIterator = null!!
+
+operator fun Double.iterator(): MyDoubleIterator = null!!
+
+operator fun Boolean.iterator(): MyBooleanIterator = null!!
+
+interface MyIntIterator {
+    operator fun hasNext(): Boolean
+    operator fun next(): Int
+}
+
+interface MyDoubleIterator {
+    operator fun hasNext(): Boolean
+    fun next(): Double
+}
+
+interface MyBooleanIterator {
+    fun hasNext(): Boolean
+    operator fun next(): Boolean
+}
+
+fun test3(i: Int, d: Double, b: Boolean) {
+    for (element in <!OPERATOR_MODIFIER_REQUIRED!>i<!>) {}
+    for (element in <!OPERATOR_MODIFIER_REQUIRED!>d<!>) {}
+    for (element in <!OPERATOR_MODIFIER_REQUIRED!>b<!>) {}
+}

compiler/testData/diagnostics/tests/Operators.txt

@@ -2,6 +2,10 @@ package
 
 public fun test(): kotlin.Unit
 public fun test2(): kotlin.Unit
+public fun test3(/*0*/ i: kotlin.Int, /*1*/ d: kotlin.Double, /*2*/ b: kotlin.Boolean): kotlin.Unit
+public operator fun kotlin.Boolean.iterator(): MyBooleanIterator
+public operator fun kotlin.Double.iterator(): MyDoubleIterator
+public fun kotlin.Int.iterator(): MyIntIterator
 
 public open class Anc : Base {
     public constructor Anc()
@@ -65,3 +69,28 @@ public final class Example2 {
     public final operator fun rangeTo(/*0*/ o: Example2): Example2
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
+
+public interface MyBooleanIterator {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun hasNext(): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public abstract operator fun next(): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface MyDoubleIterator {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract operator fun hasNext(): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public abstract fun next(): kotlin.Double
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface MyIntIterator {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract operator fun hasNext(): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public abstract operator fun next(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+

compiler/testData/diagnostics/tests/controlStructures/forWithNullableIterator.fir.kt

@@ -1,12 +0,0 @@
-class Coll {
-  operator fun iterator(): It? = null
-}
-
-class It {
-  operator fun next() = 1
-  operator fun hasNext() = false
-}
-
-fun test() {
-  for (x in <!HAS_NEXT_FUNCTION_NONE_APPLICABLE!>Coll()<!>) {}
-}

compiler/testData/diagnostics/tests/controlStructures/forWithNullableIterator.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class Coll {
   operator fun iterator(): It? = null
 }

compiler/testData/diagnostics/tests/inference/reportingImprovements/typeInferenceFailedOnIteratorCall.fir.kt

@@ -4,6 +4,6 @@ class X
 operator fun <T> X.iterator(): Iterable<T> = TODO()
 
 fun test() {
-    for (i in <!HAS_NEXT_MISSING!>X()<!>) {
+    for (i in <!HAS_NEXT_MISSING, NEXT_MISSING!>X()<!>) {
     }
 }

idea/idea-frontend-fir/idea-frontend-fir-generator/src/org/jetbrains/kotlin/idea/frontend/api/fir/generator/HLDiagnosticConverter.kt

@@ -186,6 +186,11 @@ private object FirToKtConversionCreator {
             KtSymbol::class.createType(),
             importsToAdd = listOf("org.jetbrains.kotlin.fir.declarations.FirDeclaration")
         ),
+        FirNamedFunctionSymbol::class to HLFunctionCallConversion(
+            "firSymbolBuilder.functionLikeBuilder.buildFunctionSymbol({0}.fir)",
+            KtFunctionLikeSymbol::class.createType(),
+            importsToAdd = listOf("org.jetbrains.kotlin.fir.declarations.FirSimpleFunction")
+        ),
     )
 
     private val allowedTypesWithoutTypeParams = setOf(

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.FirDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
+import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.FirTypeParameter
 import org.jetbrains.kotlin.fir.declarations.FirVariable
 import org.jetbrains.kotlin.fir.psi
@@ -630,6 +631,14 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.OPERATOR_MODIFIER_REQUIRED) { firDiagnostic ->
+        OperatorModifierRequiredImpl(
+            firSymbolBuilder.functionLikeBuilder.buildFunctionSymbol(firDiagnostic.a.fir),
+            firDiagnostic.b,
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
     add(FirErrors.INLINE_CLASS_NOT_TOP_LEVEL) { firDiagnostic ->
         InlineClassNotTopLevelImpl(
             firDiagnostic as FirPsiDiagnostic<*>,

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -17,6 +17,7 @@ import org.jetbrains.kotlin.diagnostics.WhenMissingCase
 import org.jetbrains.kotlin.idea.frontend.api.diagnostics.KtDiagnosticWithPsi
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassLikeSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtFunctionLikeSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtTypeParameterSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtVariableLikeSymbol
@@ -459,6 +460,12 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         abstract val target: String
     }
 
+    abstract class OperatorModifierRequired : KtFirDiagnostic<PsiElement>() {
+        override val diagnosticClass get() = OperatorModifierRequired::class
+        abstract val functionSymbol: KtFunctionLikeSymbol
+        abstract val name: String
+    }
+
     abstract class InlineClassNotTopLevel : KtFirDiagnostic<KtDeclaration>() {
         override val diagnosticClass get() = InlineClassNotTopLevel::class
     }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirPsiDiagnostic
 import org.jetbrains.kotlin.idea.frontend.api.fir.utils.weakRef
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassLikeSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtFunctionLikeSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtTypeParameterSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtVariableLikeSymbol
@@ -727,6 +728,15 @@ internal class WrongModifierTargetImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
+internal class OperatorModifierRequiredImpl(
+    override val functionSymbol: KtFunctionLikeSymbol,
+    override val name: String,
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.OperatorModifierRequired(), KtAbstractFirDiagnostic<PsiElement> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
 internal class InlineClassNotTopLevelImpl(
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,